More Problems On 787s Mean Turbulence For Boeing Stock

A Boeing 787 caught fire on the tarmac at London's Heathrow Airport on Friday, followed hours later by a technical problem aboard another 'Dreamliner' that forced the plane to turn back from a trans-Atlantic flight. The incidents sent Boeing's stock down more than 7 percent at one point.

The first incident involved an Ethiopian Airlines plane with no passengers aboard. The second occurred aboard a Thomson Airways flight en route from Manchester, England to Sanford, Fla.

The Ethiopian jet suffered what a Heathrow spokesman described as an "onboard internal fire" while sitting at the gate. Photographs appeared to show fire damage just forward of the tail section.

In a statement, the airline said smoke was detected coming from the plane more than eight hours after it was parked. "The aircraft was empty when the incident was observed," Ethiopian said in a brief statement. "The cause of the incident is under investigation by all concerned."

A fire in January in Boston aboard a grounded Japan Airlines 787 occurred underneath in the midsection of the fuselage, where the avionics compartment is located. It was later attributed to a faulty lithium-ion battery and forced a months-long grounding of the 50 aircraft in service around the world. While the plane was cleared to resume service in May, there have been reports of several mechanical problems since then.

In a tweet, the U.S. National Transportation Safety Board said it was sending an "accredited representative" to London-Heathrow to assist in an investigation of the latest 787 fire.

Meanwhile, U.K.-based Thomson Airways says one of its 787s traveling from England to the U.S. had to turn back on Friday after experiencing a technical issue, The Associated Press reports.

The AP quotes Thomson as saying that Flight 126 traveling from Manchester Airport to Sanford, Fla., had returned to Manchester "as a precautionary measure."